Examples of the elastic member for inkjet include an ink supply tube, an ink sealing member, a valve member, and the like. The ink supply tube for inkjet connects an ink tank to a recording head mounted on a carriage and supplies ink retained in the ink tank to the recording head. The recording head mounted on the carriage reciprocates along the carriage to perform recording on a recording medium. In recent years, an inkjet printer has been more and more downsized, and the ink supply tube is required to have high flexibility to be used in a compactly-housed fashion. Further, when a viscosity of ink is increased when the ink inside the ink supply tube is evaporated outside the ink supply tube, an issue of print quality degradation or the like is raised due to ink discharge failure or a composition change of the ink. Therefore, the ink supply tube is required to have a high water vapor barrier property. Likewise, since an ink discharge failure or an ink supply failure can occur when bubbles are generated inside the ink supply tube due to entrance of an outside gas such as air, the ink supply tube is also required to have a high air barrier property. Further, since the ink sealing member and the valve member are often used in a compressed state to prevent ink leakage, they are required to have high rubber elasticity which enables to endure the shape change.
As a material for the ink supply tube member, the ink sealing member, and the valve member, a crosslinked rubber and a thermoplastic resin have heretofore been used. However, the use of crosslinked rubber entails issues such as long-time crosslinking and molding step, difficulty in two-color molding with another member, and the like. On the other hand, since the thermoplastic resin has higher rigidity as compared to the crosslinked rubber, the thermoplastic resin is not suitable for a member which is required to have high flexibility. Accordingly, a thermoplastic elastomer is receiving attention since it enables conveniently producing a molded article by press molding, injection molding, extrusion molding, or the like and is excellent in rubber elasticity and flexibility. Examples of the thermoplastic elastomer include olefin-based, urethane-based, ester-based, styrene-based, vinyl chloride-based thermoplastic elastomers, and the like. Among these, the styrene-based thermoplastic elastomer has superior flexibility and rubber elasticity. Examples of the styrene-based thermoplastic elastomer include a styrene-butadiene-styrene triblock copolymer (SBS), a styrene-isoprene-styrene triblock copolymer (SIS), a styrene-ethylene/butylene-styrene triblock copolymer (SEBS), a styrene-ethylene/propylene-styrene triblock copolymer (SEPS), and the like. Further, in recent years, the styrene-isobutylene-styrene triblock copolymer (SIBS) has been developed.
Japanese Patent Application Laid-Open No. 2005-305878 discusses an ink supply tube for inkjet, which is obtained by using a thermoplastic elastomer. In Japanese Patent Application Laid-Open No. 2005-305878, there is a description of an example in which a material containing SIBS, polypropylene, and liquid polybutene is used as a material for the ink supply tube for inkjet. The material is excellent in water vapor barrier property and air barrier property and has good flexibility.
However, though SBS, which is a generally known styrene-based thermoplastic elastomer, has already been used for various materials including a tube material, a sealing member material, and the like, the water vapor barrier property and the air barrier property are insufficient to be used for inkjet. On the other hand, though SIBS has the water vapor barrier property, the air barrier property, and flexibility which are appropriate for use for inkjet, its moldability is low, and it is difficult to mold SIBS when used alone. Accordingly, for moldability improvement, the blending with polypropylene which has good moldability is considered as described in Japanese Patent Application Laid-Open No. 2005-305878. However, the rubber elasticity is deteriorated due to the blending with polypropylene to sometimes make it difficult to use the obtained material as the elastic member for inkjet. Further, the deterioration of rubber elasticity is prominent particularly under a high temperature environment. Further, since the inkjet members are required to have high dimension accuracy, polystyrene having a small molding shrinkage ratio and high dimension accuracy is used as a material for various component parts for inkjet. Taking thermal fusion and ultrasonic welding with such polystyrene component members into consideration, the blending with polypropylene makes it impossible to perform the welding due to the immiscibility with polystyrene.